scholarly journals Breaking the ties that bind: New advances in centrosome biology

2012 ◽  
Vol 197 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Balca R. Mardin ◽  
Elmar Schiebel
Keyword(s):  
Cell Cycle ◽  
Cancer Cells ◽  
Recent Work ◽  
Genomic Instability ◽  
Centrosome Duplication ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Centrosome Separation ◽  
Organizing Center ◽  
Pericentriolar Material

The centrosome, which consists of two centrioles and the surrounding pericentriolar material, is the primary microtubule-organizing center (MTOC) in animal cells. Like chromosomes, centrosomes duplicate once per cell cycle and defects that lead to abnormalities in the number of centrosomes result in genomic instability, a hallmark of most cancer cells. Increasing evidence suggests that the separation of the two centrioles (disengagement) is required for centrosome duplication. After centriole disengagement, a proteinaceous linker is established that still connects the two centrioles. In G2, this linker is resolved (centrosome separation), thereby allowing the centrosomes to separate and form the poles of the bipolar spindle. Recent work has identified new players that regulate these two processes and revealed unexpected mechanisms controlling the centrosome cycle.

CEP110 and ninein are located in a specific domain of the centrosome associated with centrosome maturation

2002 ◽  
Vol 115 (9) ◽  
pp. 1825-1835 ◽  
Author(s):  
Young Y. Ou ◽  
Gary J. Mack ◽  
Meifeng Zhang ◽  
Jerome B. Rattner
Keyword(s):  
Cell Cycle ◽  
Protein Interactions ◽  
Protein Function ◽  
Similar Distribution ◽  
Microtubule Organizing Center ◽  
Specific Domain ◽  
The Reformation ◽  
Mother And Daughter ◽  
Organizing Center ◽  
Pericentriolar Material

The mammalian centrosome consists of a pair of centrioles surrounded by pericentriolar material (PCM). The architecture and composition of the centrosome, especially the PCM, changes during the cell cycle. Recently, a subset of PCM proteins have been shown to be arranged in a tubular conformation with an open and a closed end within the centrosome. The presence of such a specific configuration can be used as a landmark for mapping proteins in both a spatial and a temporal fashion. Such mapping studies can provide information about centrosome organization, protein dynamics,protein-protein interactions as well as protein function. In this study, the centrosomal proteins CEP110 and ninein were mapped in relationship to the tubular configuration. Both proteins were found to exhibit a similar distribution pattern. In the mother centrosome, they were found at both ends of the centrosome tube, including the site of centrosome duplication. However,in the daughter centrosome they were present only at the closed end. At the closed end of the mother and daughter centrosome tube, both CEP110 and ninein co-localized with the centriolar protein CEP250/c-Nap1, which confirms ninein's centriole association and places CEP110 in association with this structure. Importantly, the appearance of CEP110 and ninein at the open end of the daughter centrosome occurred during the telophase-G1 transition of the next cell cycle, concomitant with the maturation of the daughter centrosome into a mother centrosome. Microinjection of antibodies against either CEP110 or ninein into metaphase HeLa cells disrupted the reformation of the tubular conformation of proteins within the centrosome following cell division and consequently led to dispersal of centrosomal material throughout the cytosol. Further, microinjection of antibodies to either CEP110 or ninein into metaphase PtK2 cells not only disrupted the tubular configuration within the centrosome but also affected the centrosome's ability to function as a microtubule organizing center (MTOC). This MTOC function was also disrupted when the antibodies were injected into postmitotic cells. Taken together, our results indicate that: (1) a population of CEP110 and ninein is located in a specific domain within the centrosome, which corresponds to the open end of the centrosome tube and is the site of protein addition associated with maturation of a daughter centrosome into a mother centrosome; and (2) the addition of CEP110 and ninein are essential for the reformation of specific aspects of the interphase centrosome architecture following mitosis as well as being required for the centrosome to function as a MTOC.

scholarly journals A two-step mechanism for the inactivation of microtubule organizing center function at the centrosome

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Jérémy Magescas ◽  
Jenny C Zonka ◽  
Jessica L Feldman
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Outer Sphere ◽  
Microtubule Organizing Center ◽  
C Elegans ◽  
Mitotic Kinases ◽  
Pulling Forces ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
Step Mechanism

The centrosome acts as a microtubule organizing center (MTOC), orchestrating microtubules into the mitotic spindle through its pericentriolar material (PCM). This activity is biphasic, cycling through assembly and disassembly during the cell cycle. Although hyperactive centrosomal MTOC activity is a hallmark of some cancers, little is known about how the centrosome is inactivated as an MTOC. Analysis of endogenous PCM proteins in C. elegans revealed that the PCM is composed of partially overlapping territories organized into an inner and outer sphere that are removed from the centrosome at different rates and using different behaviors. We found that phosphatases oppose the addition of PCM by mitotic kinases, ultimately catalyzing the dissolution of inner sphere PCM proteins at the end of mitosis. The nature of the PCM appears to change such that the remaining aging PCM outer sphere is mechanically ruptured by cortical pulling forces, ultimately inactivating MTOC function at the centrosome.

scholarly journals Nudel Contributes to Microtubule Anchoring at the Mother Centriole and Is Involved in Both Dynein-dependent and -independent Centrosomal Protein Assembly

2006 ◽  
Vol 17 (2) ◽  
pp. 680-689 ◽  
Author(s):  
Jing Guo ◽  
Zhenye Yang ◽  
Wei Song ◽  
Qi Chen ◽  
Fubin Wang ◽  
...  
Keyword(s):  
Hela Cells ◽  
Cytoplasmic Dynein ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Centrosomal Protein ◽  
Centriole Duplication ◽  
Mother Centriole ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
New Mother

The centrosome is the major microtubule-organizing center in animal cells. Although the cytoplasmic dynein regulator Nudel interacts with centrosomes, its role herein remains unclear. Here, we show that in Cos7 cells Nudel is a mother centriole protein with rapid turnover independent of dynein activity. During centriole duplication, Nudel targets to the new mother centriole later than ninein but earlier than dynactin. Its centrosome localization requires a C-terminal region that is essential for associations with dynein, dynactin, pericentriolar material (PCM)-1, pericentrin, and γ-tubulin. Overexpression of a mutant Nudel lacking this region, a treatment previously shown to inactivate dynein, dislocates centrosomal Lis1, dynactin, and PCM-1, with little influence on pericentrin and γ-tubulin in Cos7 and HeLa cells. Silencing Nudel in HeLa cells markedly decreases centrosomal targeting of all the aforementioned proteins. Silencing Nudel also represses centrosomal MT nucleation and anchoring. Furthermore, Nudel can interact with pericentrin independently of dynein. Our current results suggest that Nudel plays a role in both dynein-mediated centripetal transport of dynactin, Lis1, and PCM-1 as well as in dynein-independent centrosomal targeting of pericentrin and γ-tubulin. Moreover, Nudel seems to tether dynactin and dynein to the mother centriole for MT anchoring.

scholarly journals Superresolution characterization of core centriole architecture

2021 ◽  
Vol 220 (4) ◽  
Author(s):  
Yuan Tian ◽  
Chenxi Wei ◽  
Jianfeng He ◽  
Yuxuan Yan ◽  
Nan Pang ◽  
...  
Keyword(s):  
Outer Layer ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Protein Architecture ◽  
Symmetrical Pattern ◽  
C Terminus ◽  
Direct View ◽  
Organizing Center ◽  
Pericentriolar Material

The centrosome is the main microtubule-organizing center in animal cells. It comprises of two centrioles and the surrounding pericentriolar material. Protein organization at the outer layer of the centriole and outward has been studied extensively; however, an overall picture of the protein architecture at the centriole core has been missing. Here we report a direct view of Drosophila centriolar proteins at ∼50-nm resolution. This reveals a Sas6 ring at the C-terminus, where it overlaps with the C-terminus of Cep135. The ninefold symmetrical pattern of Cep135 is further conveyed through Ana1–Asterless axes that extend past the microtubule wall from between the blades. Ana3 and Rcd4, whose termini are close to Cep135, are arranged in ninefold symmetry that does not match the above axes. During centriole biogenesis, Ana3 and Rcd4 are sequentially loaded on the newly formed centriole and are required for centriole-to-centrosome conversion through recruiting the Cep135–Ana1–Asterless complex. Together, our results provide a spatiotemporal map of the centriole core and implications of how the structure might be built.

scholarly journals Centriole-less pericentriolar material serves as a microtubule organizing center at the base of C. elegans sensory cilia

2020 ◽  
Author(s):  
Jérémy Magescas ◽  
Sani Eskinazi ◽  
Michael V. Tran ◽  
Jessica L. Feldman
Keyword(s):  
Sensory Neurons ◽  
Super Resolution ◽  
Spatial Separation ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Tissue Specific ◽  
C Elegans ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
Specific Degradation

SummaryDuring mitosis in animal cells, the centrosome acts as a microtubule organizing center (MTOC) to assemble the mitotic spindle. MTOC function at the centrosome is driven by proteins within the pericentriolar material (PCM), however the molecular complexity of the PCM makes it difficult to differentiate the proteins required for MTOC activity from other centrosomal functions. We used the natural spatial separation of PCM proteins during mitotic exit to identify a minimal module of proteins required for centrosomal MTOC function in C. elegans. Using tissue specific degradation, we show that SPD-5, the functional homolog of CDK5RAP2, is essential for embryonic mitosis while SPD-2/CEP192 and PCMD-1, which are essential in the zygote, are dispensable. Surprisingly, although the centriole is known to be degraded in the ciliated sensory neurons in C. elegans [1-3], we find evidence for “centriole-less PCM” at the base of cilia and use this structure as a minimal testbed to dissect centrosomal MTOC function. Super-resolution imaging revealed that this PCM inserts inside the lumen of the ciliary axoneme and directly nucleates the assembly of dendritic microtubules towards the cell body. Tissue-specific degradation in ciliated sensory neurons revealed a role for SPD-5 and the conserved microtubule nucleator γ-TuRC, but not SPD-2 or PCMD-1, in MTOC function at centriole-less PCM. This MTOC function was in the absence of regulation by mitotic kinases, highlighting the intrinsic ability of these proteins to drive microtubule growth and organization and further supporting a model that SPD-5 is the primary driver of MTOC function at the PCM.

scholarly journals A two-step mechanism for the inactivation of microtubule organizing center function at the centrosome

2018 ◽  
Author(s):  
Jérémy Magescas ◽  
Jennifer C. Zonka ◽  
Jessica L. Feldman
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Microtubule Organizing Center ◽  
Step Process ◽  
C Elegans ◽  
Pulling Forces ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
And Behavior ◽  
Step Mechanism

SummaryDuring mitosis, the centrosome acts as a microtubule organizing center (MTOC), orchestrating microtubules into the mitotic spindle through its pericentriolar material (PCM). This activity is biphasic, cycling through assembly and disassembly during the cell cycle. Although hyperactive centrosomal MTOC activity is a hallmark of some cancers, little is known about how the centrosome is inactivated as an MTOC. Analysis of endogenous PCM proteins in C. elegans revealed that the PCM is composed of distinct protein territories that are removed from the centrosome at different rates and using different behaviors. Inhibition of PP2A phosphatases stabilized the PCM and perturbation of cortical pulling forces altered the timing and behavior by which proteins were removed from the centrosome. These data indicate that PCM disassembly is a two-step process, beginning with a phosphatase-dependent dissolution of PCM proteins followed by the ejection of ruptured PCM by cortical forces, ultimately inactivating MTOC function at the centrosome.

scholarly journals PLK4 is a microtubule-associated protein that self assembles promoting de novo MTOC formation

2018 ◽  
Author(s):  
Susana Montenegro Gouveia ◽  
Sihem Zitouni ◽  
Dong Kong ◽  
Paulo Duarte ◽  
Beatriz Ferreira Gomes ◽  
...  
Keyword(s):  
De Novo ◽  
Supramolecular Assemblies ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
Xenopus Egg ◽  
Summary Statement ◽  
Β Tubulin

Summary statementPLK4 binds to microtubules and self assembles into supramolecular assemblies that recruit tubulin and trigger de novo MTOC formation in Xenopus laevis extracts.AbstractThe centrosome is an important microtubule-organizing center (MTOCs) in animal cells and it consists of two barrel-shaped structures (centrioles), surrounded by the pericentriolar material (PCM), which nucleates microtubules. PCM components form condensates, supramolecular assemblies that concentrate microtubule nucleators. Centrosomes can form close to an existing structure (canonical duplication) or de novo. How centrosomes form de novo is not known. PLK4 is a master driver of centrosome biogenesis, which is critical to recruit several centriole components. Here, we investigate the beginning of centrosome biogenesis, taking advantage of Xenopus egg extracts, where we and others have shown that PLK4 can induce de novo MTOC formation (Eckerdt et al., 2011; Zitouni et al., 2016). Surprisingly, we observe that in vitro, PLK4 can self-assemble into supramolecular assemblies that recruit α/β-tubulin. In Xenopus extracts, PLK4 supramolecular assemblies additionally recruit the PLK4 substrate STIL and the microtubule nucleator, γ-tubulin, and form acentriolar MTOCs de novo. The assembly of these robust microtubule asters is independent of dynein, similarly to centrosomes. We suggest a new mechanism of action for PLK4, where it forms a self-organizing catalytic scaffold that recruits centriole components, PCM factors and α/β-tubulin, leading to MTOC formation.

scholarly journals Centriole-independent centrosome assembly in interphase mammalian cells

2021 ◽  
Author(s):  
Fangrui Chen ◽  
Jingchao Wu ◽  
Malina K. Iwanski ◽  
Daphne Jurriens ◽  
Arianna Sandron ◽  
...  
Keyword(s):  
Self Assembly ◽  
Mammalian Cells ◽  
Self Organization ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
Self Association

The major microtubule-organizing center (MTOC) in animal cells, the centrosome, comprises a pair of centrioles surrounded by pericentriolar material (PCM), which nucleates and anchors microtubules. Centrosome assembly depends on the interactions of PCM with centrioles, PCM self-association and dynein-mediated transport. Here, we show that if centrioles are lost due to PLK4 depletion or inhibition, PCM still forms a single centrally located MTOC when non-centrosomal microtubule minus end organization pathways are disabled. Acentriolar MTOC assembly depends on dynein-driven coalescence of PCM clusters with attached microtubule minus ends and requires γ-tubulin, pericentrin, CDK5RAP2 and ninein, but not NEDD1, CEP152 or CEP192. PCM self-assembly is inhibited by AKAP450-dependent PCM recruitment to the Golgi and by CAMSAP2-mediated microtubule minus end stabilization. However, if CAMSAP2 is linked to a minus-end-directed motor, a single MTOC containing PCM components can still form, and its organization depends on the presence of pericentrin. Our results reveal that the formation of a single central MTOC in interphase mammalian cells is not strictly centriole dependent but can be driven by self-organization of PCM and microtubule minus ends.

Three-Dimensional reconstruction of isolated centrosomes by automated electron tomography

1994 ◽  
Vol 52 ◽  
pp. 310-311
Author(s):  
M.B. Braunfeld ◽  
M. Moritz ◽  
B.M. Alberts ◽  
J.W. Sedat ◽  
D.A. Agard
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Vital Role ◽  
Complex Nature ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Nucleation Sites ◽  
Dimensional Reconstruction ◽  
Organizing Center ◽  
Resolution Model

In animal cells, the centrosome functions as the primary microtubule organizing center (MTOC). As such the centrosome plays a vital role in determining a cell's shape, migration, and perhaps most importantly, its division. Despite the obvious importance of this organelle little is known about centrosomal regulation, duplication, or how it nucleates microtubules. Furthermore, no high resolution model for centrosomal structure exists.We have used automated electron tomography, and reconstruction techniques in an attempt to better understand the complex nature of the centrosome. Additionally we hope to identify nucleation sites for microtubule growth.Centrosomes were isolated from early Drosophila embryos. Briefly, after large organelles and debris from homogenized embryos were pelleted, the resulting supernatant was separated on a sucrose velocity gradient. Fractions were collected and assayed for centrosome-mediated microtubule -nucleating activity by incubating with fluorescently-labeled tubulin subunits. The resulting microtubule asters were then spun onto coverslips and viewed by fluorescence microscopy.

scholarly journals The role of Aspergillus nidulans polo-like kinase PlkA in microtubule-organizing center control

2021 ◽  
Author(s):  
Xiaolei Gao ◽  
Saturnino Herrero ◽  
Valentin Wernet ◽  
Sylvia Erhardt ◽  
Oliver Valerius ◽  
...  
Keyword(s):  
Aspergillus Nidulans ◽  
Cell Types ◽  
Spindle Pole ◽  
Receptor Protein ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Spindle Pole Bodies ◽  
Organizing Center ◽  
Ring Complex ◽  
Core Components

Centrosomes are important microtubule-organizing centers (MTOC) in animal cells. In addition, non-centrosomal MTOCs (ncMTOCs) were described in many cell types. Functional analogs of centrosomes in fungi are the spindle pole bodies (SPBs). In Aspergillus nidulans additional MTOCs were discovered at septa (sMTOC). Although the core components are conserved in both MTOCs, their composition and organization are different and dynamic. Here, we show that the polo-like kinase PlkA binds the γ-tubulin ring complex (γ-TuRC) receptor protein ApsB and contributes to targeting ApsB to both MTOCs. PlkA coordinates SPB outer plaque with sMTOC activities. PlkA kinase activity was required for astral MT formation involving ApsB recruitment. PlkA also interacted with the γ-TuRC inner plaque receptor protein PcpA. Mitosis was delayed without PlkA, and the PlkA protein was required for proper mitotic spindle morphology, although this function was independent of its catalytic activity. Our results suggest polo-like kinase as a regulator of MTOC activities and as a scaffolding unit through interaction with γ-tubulin ring complex receptors.

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